The overarching goal of the proposed research is to define the cellular, molecular and metabolic mechanisms determining the response of the heart to myocardial ischemia and LV pressure overload, in order to develop novel therapeutic approaches for patients with cardiovascular disease. Our group discovered that macrophage migration inhibitory factory (MIF) is secreted from the heart during ischemia-reperfusion, activating AMP- activated protein kinase (AMPK) and constituting a protective autocrine-paracrine pathway. The protective action of MIF is mediated by the cell surface CD74 receptor. However, MIF has additional pleiotropic effects to activate the chemokine receptors CXCR2/4, which may be detrimental during pathophysiological stress and render it less than ideal for therapeutic development. We have recently discovered a non-redundant second ligand for CD74 called D-dopachrome tautomerase (DDT), which is more selective than MIF for the CD74 receptor. Our initial results indicate that cardiomyocyte-derived DDT has important actions to prevent both injury during ischemic-reperfusion and heart failure consequent to LV pressure overload. Our Chemical Biology group has also designed small molecule agonists that specifically facilitate activation of CD74. Thus, we will study the molecular signaling and physiological effects of these reagents in the heart and then investigate their therapeutic potential in ischemia-reperfusion. Our specific aims are 1) to determine the signaling mechanisms that mediate DDT action downstream to CD74, 2) to determine the role of endogenous cardiomyocyte-derived DDT in regulating the response of the heart to pathological stress, and 3) to develop and optimize the CD74 pathway as a therapeutic strategy in the heart. Understanding CD74 signaling has broad implications for patients with cardiovascular disease, but might have particular significance in specific individuals who have an increased susceptibility to ischemia in the heart and potentially other solid organs. Such patients include those with a common polymorphism (>5%) in the human MIF promoter, which we have shown leads to impaired MIF secretion and CD74-dependent AMPK activation during hypoxia. The elderly might also benefit, since the MIF- CD74-AMPK axis is also impaired with aging in mice. We have assembled a multi-disciplinary team with expertise in the areas of cellular metabolism and signaling, ischemic heart disease, MIF biology, inflammatory disease, recombinant protein and chemical synthesis. We have generated novel recombinant proteins, small molecule activators, antibodies and genetic mouse models to enable us to test whether the strategy of CD74 receptor activation is protective. Thus, we are poised to define novel biological pathways in ischemic heart disease and develop translational strategies that have potential to result in new treatment strategies for patients with cardiovascular disease.